Conventionally, there is a well-known vehicle seat including a seat back frame, a collision sensor which is provided to the seat back frame and moves backward when a seat occupant is moved relatively backward to the seat back frame due to a rear-end collision, and a headrest which is attached to the seat back frame and is movable between a normal support position and a head protection position anterior to the normal support position, and which moves from the normal support position to the head protection position when the collision sensor is moved backward.    [Patent Document 1] Japanese Patent Application Laid-Open No, 10-119619